Galactic Time-Keeping: Creating a Universal Calendar

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In summary, the problem with the two questions is that they lack a coherent concept of what 'galactic time' would be. Neither question specifies what sort of standard or mechanism would be needed to keep track of the timing.
  • #1
sozme
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Here are two related problems I was thinking about and wonder if you can chime in (didn't see any related threads on these issues already):

1. Say there is a galactic "community" made-up of various species of sentient beings (humans being one of them). Say they have a central meeting place where political affairs are discussed, treaties are signed, etc. The question is this: Would such an arrangement require a sort of universal time-keeping standard? I.e. how would the humans arrange a meeting with aliens on the other side of the galaxy?

Of course they wouldn't say, "Ok, let's meet at point X on Wednesday at 5:00pm" since outside of Earth the 24 hour clock and Gregorian calendar are completely meaningless, and probably other reasons you guys know about that I do not. This is a big problem I have run into and I don't even know if I'm thinking of it in the right terms.

I would think that a galactic community that has to arrange meetings and schedule things would have some sort of universal, objective standard of time and date that could be easily referenced. Any one have any ideas or thoughts on this?

2. Say there are a number of human colonies located on various exoplanets separated by tens of thousands of light years. Forgetting how they actually got there in the first place, let's say they have some sort of central government (in addition to their planetary, national, local governments, etc.)

What ways might a civilization like this maintain an objective calendar-keeping system? I assume that if whatever the capital world of such a civilization would create a new calendar based on the orbital period of their own star, but would do you think this would be absolutely necessary?
 
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  • #2
None of your questions make any sense without the existence of faster than light communications and/or travel and since those don't exist and are believed to be impossible, I don't see how there can be any meaningful answers to your questions.
 
  • #3
Some multiple of plank seconds I would think.
 
  • #4
schonovic said:
Some multiple of plank seconds I would think.
Yes, that would make sense to record the PASSAGE of time but has nothing to do with the OP's question of how do you establish a synchronized galactic standard for what TIME it is.
 
  • #5
schonovic said:
Some multiple of plank seconds I would think.
Are those measured or written on a flat board? I would think Planck seconds would be better.
 
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  • #6
I don't see the problem. You send a message to the Little Green Men that says "These are seconds. One. Two. Three. In 864,000 of them, please meet us on Remulak".
 
  • #7
Yeah, I'm with Vanadium on this. Much easier for each planet to stick to local days and years, or what makes sense to them. It seems more sensible to use simple conversion algorithm to translate dates other planets are using than enforce arbitrary unified time scheme.
It's not that much different from the issue of metric and imperial systems we have to deal with, only on a much larger scale.
 
  • #8
Consider that the galaxy is 100,000 light years across. Say I want to schedule a meeting. In order for me to notify the whole galaxy AND give them reasonable time to come to the meeting place, I better set that meeting ~200,000 years in the future. And this is assuming that the inhabitants of the galaxy can travel very close to the speed of light. :D

In addition, participants from the other side of the galaxy can expect a 200,000 year round trip journey to attend my meeting...so this better be a pretty darn important meeting!
 
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  • #9
So far the answers seem to be only considering the scale of "galactic time" and not how it would be synchronised. For accurate timing, there would have to be some agreement on a rest frame.

On the other aspect of faster-than-light communication, it is known scientifically that if faster than light travel is possible relative to an arbitrary inertial frame of reference, then this leads to causality violation, and it seems reasonable to assume that this means it is impossible. However, there is no similar scientific disproof of the possibility of communication or travel at unlimited speed relative to some universally synchronised preferred frame, which is usually called "subspace" in science fiction. At present, there is no experimental evidence for such a preferred frame, so we assume it does not exist, and we do not know of anything which currently violates the principle of relativity in this way. However, it is sometimes used for example as part of a model for explaining quantum entanglement, and I think that for purposes of science fiction on a galactic scale the "subspace" idea seems quite acceptable.
 
  • #10
even with the ability to travel from one point to another with a reasonable delay (not in 100's or 10's of thousands of years) each group would need a form of communication learned by all. including math which would allow for a standard of time passage each could agree on.
 
  • #11
I always liked Alfred Bester's solution in 'The stars my destination' - jaunting - an innate human ability to teleport oneself instantly, even across the voids of space. Solves lots of problems like the ones mentioned above. Heck I reread it 30 years ago, so I guess I'm due for a reread now.
 
  • #12
Jonathan Scott said:
So far the answers seem to be only considering the scale of "galactic time" and not how it would be synchronised. For accurate timing, there would have to be some agreement on a rest frame.
No there doesn't. This isn't any more complicated than arranging meetings in different time zones: Let's meet at 2:00 pm EST (Eastern Standard Time). By stating the time zone I'm meausuring the time in I've specified myself to be the rest/preferred frame. If I want to be nice for a client in California, I might specify that we have the meeting at 11:00 am PST, doing the conversion for him and specifying him to be the rest/preferred frame.

Now, interstellar meetings would be problematic without FTL communications, but that's a problem that exists independent of the preferred frame issue. I can specify that the meeting be in person or if it requires only a one way communication (tell me if you like cheese), I can specify when, in my frame, I want the answer and you'll have to calculate when to send it.
 
  • #13
This subject is the very reason that Gene Roddenberry "invented" the Stardate system used in the Star Trek franchise; it was meant to be not only a universal reference, but also one that took into account relativistic time dilation during space flight. (Of course, he never explained how it worked... :rolleyes:)
 
  • #14
You know I think there is a kind of expectation of thinking of a great idea to solve the problem.

If there is a place of some special significance - then we just count the passage of time in that one place.

For practical purposes - how many different time standards there would be. 1000? OK. How big would be a standard record about each time measurement method? 1KB?
So I can either hope for:
1) effective intergalactic cooperation and lack of chauvinism;
2) a simple converter application in my mobile phone that would need one megabyte of free place.
 
  • #15
Why not use the rotation of the galaxy as a frame of reference? The galaxy has a defined rotational speed, creating a time system based on revolutions our own galaxy since an agreed upon beginning of time (The Big Bang) would seem feasible. I mean, you'd be measuring the rotation based on a mathematical equivalency to each Race's preferred unit of measurement, but a standard of time could technically be agreed upon, based on the rotational speed of the galaxy and how many times it completes a full cycle.
 
  • #16
Czcibor said:
For practical purposes - how many different time standards there would be. 1000?
That seems a bit optimistic, since we have a couple of dozen on Earth alone.
 
  • #17
guess the fairly stable cycles of a pulsar could be used as a interstellar clock as long as each participant can actually see the same pulsar.
 
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  • #18
dragoneyes001 said:
guess the fairly stable cycles of a pulsar could be used as a interstellar clock as long as each participant can actually see the same pulsar.
That might be about the closest thing available. It still wouldn't be absolute, though, because a pulsar's period varies over time and it will appear to spin faster the farther one is from it due to "speed of light" observational lag.

edit: On the other hand... hmmm... I suppose that such could be compensated for simply by maintaining knowledge of how far one is from it when the observation is made.
 
  • #19
Instead of a pulsar, you can also use an atomic clock and transmit the time signal to the whole galaxy. Sure, you have to take signal delays into account.
This is not a new concept, we use the same approach in the solar system already (with signal delays of several hours for the Voyager probes and New Horizons).

You can then convert this universal time to local time standards.
 
  • #20
mfb said:
Instead of a pulsar, you can also use an atomic clock and transmit the time signal to the whole galaxy. Sure, you have to take signal delays into account.
Of course, if other civilizations are anything like ours, it will never happen. It would take until the end of the Universe for the various cultures to decide upon which pulsar or atomic clock to use. :rolleyes:
 
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  • #21
dragoneyes001 said:
guess the fairly stable cycles of a pulsar could be used as a interstellar clock as long as each participant can actually see the same pulsar.
Interesting, could you expand on that? What are the stable cycles of a pulsar?
 
  • #22
Danger said:
Of course, if other civilizations are anything like ours, it will never happen. It would take until the end of the Universe for the various cultures to decide upon which pulsar or atomic clock to use. :rolleyes:
It worked on earth. For more than 95% of the world population and more than 99% of the science done.

Oh, I can certainly imagine a galaxy, using a common unit system everywhere apart from the US.

cbrons said:
Interesting, could you expand on that? What are the stable cycles of a pulsar?
The pulse frequency (that's why they are called pulsars).
 
  • #23
mfb said:
It worked on earth. For more than 95% of the world population and more than 99% of the science done.
After how many thousands of years of trying? (Or maybe hundreds; it escalated every time people discovered that there was more planet out there than they were previously aware of.) Time zones weren't invented until the 1800's. Ship chronometers came earlier, based upon their "home" time, but that was for commercial and political reasons more than scientific ones. Even now there's some ambiguity regarding things such as marine time (not to the experts, but to laymen). And we're all of the same species sharing almost all of the same DNA and the same environment with it's rotations and revolutions and axial tilts. It would probably take several hundred years just to come up with enough common language to express what is meant by certain terms. What would a species with no limbs use as counting units? If they can't detect light, would they have any concept of a day/night cycle?
I'm not trying to imply that such can't happen; it's merely that we will have to have advanced an awful lot socially as well as scientifically before such a thing can take place, and so would the other civilizations involved.
(Really, now... it can take over a year to set the seating arrangement at a meeting to everyone's satisfaction.)
 
  • #24
Danger said:
After how many thousands of years of trying?
What is the point? Learning to control fire took very long, but our ancestors did it, and we can use it since then.
Danger said:
It would probably take several hundred years just to come up with enough common language to express what is meant by certain terms.
It depends on the type of contact, but mathematics and physics are surprisingly easy to express in a way other intelligent species should understand.
Danger said:
What would a species with no limbs use as counting units?
Why would you need limbs to understand the concept of "3" as in "3 objects on the floor"?
Danger said:
If they can't detect light, would they have any concept of a day/night cycle?
They don't need one, our definition of a second is independent of it, too. To reach the level of interstellar communication, they would need some sort of time unit, and conversion factors are easy to apply.
 
  • #25
mfb said:
Why would you need limbs to understand the concept of "3" as in "3 objects on the floor"?
I just meant that we began with decimal because of our digits, and other common bases such as octal and hex are built upon binary. If the aliens have tentacles, they might use base 7.
mfb said:
don't need one, our definition of a second is independent of it, too.
That was to point out how much of our culture, and even the progression of our science, arose from the day/night and yearly cycles as to agriculture development. That was one of the most important concepts of timekeeping.
 
  • #26
Danger said:
I just meant that we began with decimal because of our digits, and other common bases such as octal and hex are built upon binary. If the aliens have tentacles, they might use base 7.
So what? All our computers work with base 2. As you can see, the conversion works so well we don't even notice it.
That was to point out how much of our culture, and even the progression of our science, arose from the day/night and yearly cycles as to agriculture development. That was one of the most important concepts of timekeeping.
Sure, but we do not need it for a unit of time.
 
  • #27
You're proving my point all along. If we can't even agree on this, what makes you think that a sulfur-based lifeform from a gas-giant planet would agree with either of us?
 
  • #28
Maybe we mean different things with "agree".
I don't suggest that the whole galaxy would abandon all but one time system. That would be highly impractical.
I say the whole galaxy could work with a single time system for communication and other issues that is understood everywhere, and keep their local time systems in parallel, without conversion problems.
 
  • #29
Oh, okay. Agreed. I still think that it would take a long time to establish a system, but if scientists are in charge rather than politicians it should be doable.
I was just thinking back a few years to when some big UN thing like missile talks or something was put off for six months while they argued about what shape the table should be.
 
  • #30


Arquillian battle rules, kid: first we get an ultimatum, then a warning shot, then we have a galactic standard week to respond.

A galactic standard week? How the hell long is that?

One hour.
 
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  • #31
Because of how accurate it's been possible to make atomic clocks, we now face a similar problem here on the Earth's surface and low Earth orbit, especially with the Global Positioning Satellites (GPS).

First, there's the question of the definition of time in general relativity, with its curved space-time. Viable GR alternatives like Generalized Brans-Dicke feature the same sort of curvature, but with different source terms, so this discussion will carry over into them. Every entity has its own proper time, but that alone gives us no way of relating them. Instead, one must define time in a way that gives every space-time point a well-defined time. Thus, time is defined from a foliation or splitting up of space-time into spacelike 3-hypersurfaces, where each hypersurface has a time value associated with it. For flat space-time, it is easy. The standard definition of time there involves flat and parallel 3-hypersurfaces, with time changing at constant rate in an orthogonal direction. Most GR definitions try to approximate that definition to within the limits of space-time curvaure. If there is a time-translation symmetry, as with the Schwarzschild and Kerr black-hole solutions, then one can use it to define an overall time. Likewise, the FLRW cosmology metric has a well-defined overall time in it.

Our Galaxy, like the Earth and its neighborhood, are well within the weak-field limit, so one must use a post-Newtonian expansion to define a standard foliation and a time coordinate. But there seems to be a generally-accepted foliation, one that makes the space-time metric look like the usual statement of the Parametrized Post-Newtonian metric. It's close to the flat-spacetime one.

But those preliminaries aside, let us look at Earth timekeeping.

Astronomers started out by using the Earth's rotation, but the orbits of the Moon and the planets showed variations that were closely parallel, so they switched to Ephemeris Time, the time associated with those orbits. The Earth's rotation's irregularities is what those variations were. Then in the 1960's, humanity had gotten laboratory clocks that could compete with astronomical measurements: atomic clocks. They now use as a reference International Atomic Time (TAI, from its French initials), kept by some 300 atomic clocks in some 30 national laboratories. Their measured times are compared to each other to get a more precise standard than any individual one.

TAI is intended as a realization of Terrestrial Time (English and French initials the same), the time at the Earth's sea-level surface (the "geoid").

This time can be extrapolated to infinity relative to the Earth while ignoring other objects, yielding Geocentric Coordinate Time (TCG). It flows faster than TT does, with an additional factor of 7.0*10-10, meaning that clocks at infinity would look fast by that additional factor relative to the Earth's surface. That's about 22 milliseconds/year.

One can do the same with the Earth and the Solar System. Its Barycentric Coordinate Time (TCB) flows faster than Earth-surface time by an additional factor of about 1.6*10-8. That's about half a second per year.

Doing that with the Solar System and our Galaxy yields an additional factor of about 10-6 for extragalactic vs. Solar-System time. That's about 30 seconds/year. Over a century, that adds up to about an hour.

So time-rate variations within our Galaxy are not going to be very noticeable unless one does very precise timekeeping.
 
  • #32
lpetrich said:
So time-rate variations within our Galaxy are not going to be very noticeable unless one does very precise timekeeping.
We frequently add leap seconds at the end of a year, so apparently we do.
 
  • #33
mfb said:
We frequently add leap seconds at the end of a year, so apparently we do.

Leap seconds don't affect the long term atomic time, TAI, but rather affect how we adjust UTC to match the slightly varying rotation of the earth.
 
  • #34
Sure, I mentioned the leap seconds as an example that a difference of fractions of a second per year is so much we don't want it to influence our timekeeping. An atomic clock on moon or Mars would need a different tune to keep in sync with our clocks on earth, in the same way the GPS clocks have to take care about that.
 
  • #35
TAI is an approximation of TT, Terrestrial Time, which is the proper time of a point on the geoid. That's the equal-potential surface that roughly corresponds to the Earth's sea-level surface.

To refer to its counterpart on Mars, one converts to the Solar System's coordinate time, TDB, along the way: (Earth) -> TDB -> (Mars)
 
<h2>1. What is galactic time-keeping?</h2><p>Galactic time-keeping is a system of measuring time that takes into account the rotations, revolutions, and movements of celestial bodies in our galaxy.</p><h2>2. Why is a universal calendar necessary?</h2><p>A universal calendar helps to standardize time measurements and allows for easier communication and coordination across different cultures and time zones. It also helps in scientific calculations and observations.</p><h2>3. How is a universal calendar created?</h2><p>A universal calendar is created by determining a common unit of time, such as a day or year, and then aligning it with the movements of celestial bodies. This involves using precise measurements and calculations to determine the length of a day or year on a universal scale.</p><h2>4. What are some challenges in creating a universal calendar?</h2><p>One challenge is determining a common unit of time that can be universally recognized and accepted. Another challenge is accounting for the differences in the rotations and revolutions of celestial bodies in different parts of the galaxy.</p><h2>5. How accurate is a universal calendar?</h2><p>The accuracy of a universal calendar depends on the precision of the measurements and calculations used to create it. With advancements in technology and scientific understanding, a universal calendar can be extremely accurate, but there may always be slight variations due to the complexities of the movements of celestial bodies.</p>

1. What is galactic time-keeping?

Galactic time-keeping is a system of measuring time that takes into account the rotations, revolutions, and movements of celestial bodies in our galaxy.

2. Why is a universal calendar necessary?

A universal calendar helps to standardize time measurements and allows for easier communication and coordination across different cultures and time zones. It also helps in scientific calculations and observations.

3. How is a universal calendar created?

A universal calendar is created by determining a common unit of time, such as a day or year, and then aligning it with the movements of celestial bodies. This involves using precise measurements and calculations to determine the length of a day or year on a universal scale.

4. What are some challenges in creating a universal calendar?

One challenge is determining a common unit of time that can be universally recognized and accepted. Another challenge is accounting for the differences in the rotations and revolutions of celestial bodies in different parts of the galaxy.

5. How accurate is a universal calendar?

The accuracy of a universal calendar depends on the precision of the measurements and calculations used to create it. With advancements in technology and scientific understanding, a universal calendar can be extremely accurate, but there may always be slight variations due to the complexities of the movements of celestial bodies.

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